Conveyor systems are the backbone of any production line, moving raw materials to assembly stations, partially finished goods through various processing stations, and finished goods to storage. If a conveyor system breaks down, all operations associated with that system must cease while the problem is located and corrected. And, because the outputs from one conveyor line may be used as the inputs for another line, problems with one conveyor may have an impact upon operations throughout a plant. Each minute that a system is down, labor and equipment remain idle, and this increases production costs and decreases the efficiency of an operation. Clearly, it is important to keep conveyors running continuously and to correct any problems that do occur as quickly as possible.
Many conveyor systems include a power chain that is connected to a drive mechanism. The ends of the chain are connected to each other to form an endless loop, and the chain is passed around a drive sprocket and driven about a pathway. As used herein, the term "chain" is intended to include both traditional chains of interconnected metal or plastic links, and belts, cables as well as other arrangements capable of being used like a chain. A conveyor belt or independent carriers may be connected directly to the chain, or more often, the power chain will be used to push trolleys or other carriers along a "free" track closely spaced from the power chain. In such a power and free system, pusher elements are connected directly to the driving chain and extend a short distance away from the power chain to contact pusher dogs on the carriers. The carriers are pushed along the free track by the pushers, and when it is desired to stop a carrier, the pusher dog on the carrier is retracted and the carrier stops. In this manner, the motion of each carrier can be controlled independently. Carriers, such as trolleys, may also be configured so that the impact between a moving trolley and a trolley that has been stopped downstream of the moving trolley will disengage the moving trolley from the pusher and power chain.
Conveyor systems are prone to jamming, and jam conditions can be difficult to locate, especially when the power chain is substantially enclosed in a housing. Jams can occur in many ways. A jam might be caused by a foreign object that becomes lodged between the housing and the power chain, or by a kink in the chain, possible caused by insufficient lubrication, which kink becomes jammed in a turn or in a portion of the housing. Jams can also occur when a pusher contacts a part of the power chain housing or a fixed object that has been placed too close to the power chain. Finally, a jam can occur when a trolley does not properly disengage from the power chain, such as when it is being accumulated with other carriers at a stopping location on the track. When a jam occurs the conveyor system stops, but there is generally no way of knowing what kind of jam is present.
A conveyor system may be hundreds or even thousands of feet long. When the system jams it comes to a stop, and it can be very difficult to determine even generally where the jam is located. The carriers and their spacings can be examined first, and this requires a visual examination of the entire length of the track. If the problem is not caused by a carrier jam, then the entire length of the chain must be inspected. This examination is made more difficult when, as is often the case, the chain is partly or substantially enclosed by a housing which prevents the chain from being easily seen. Many jams can be quickly corrected once they are located, but locating a jam is a time consuming process. It would therefore be desirable to provide a jam detection system and method for identifying the location of a jam when it occurs to minimize the examination process which has heretofore been necessary to find the jam location.